arm64: dts: qcom: sc8180x: Add missing CPU<->MDP_CFG path

To guarantee the required resources are enabled, describe the
interconnect path between the MDSS and the CPU.

Fixes: 494dec9b ("arm64: dts: qcom: sc8180x: Add display and gpu nodes")
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20231230-topic-8180_more_fixes-v1-8-93b5c107ed43@linaro.org


Signed-off-by: Bjorn Andersson <andersson@kernel.org>